By Frank Ramos
Published: June 25, 2010
The potential for bioremedial activities of microorganisms in polluted marine sediments is the fundamental approach that must be considered to cost effectively restore the marine ecosystem. The Horizon oil spill is a disaster that could be greatly mitigated with the proper use of bioremediation techniques. The ocean and coastal areas are excellent arenas for the use of bioremediation. Trillions of hungry, gluttonous microbes can economically devour the contamination in the beaches and marches if the proper conditions are maintained after the addition of effective acclimated microorganisms.
Microorganisms specifically acclimated to degrade crude oil breaks down the carbon chains and use it as food until the contaminant is totally eliminated; when the food source is finished, the microbes die. Bioremediation has been shown to be effective in both the Exxon Valdez spill and the Gulf War cleanup [a]. Application of bioremediation and effective treatment methods are well documented in the literature.
Chemical analysis before, during, and after application of bioremediation techniques are required to monitor the removal of toxins. Total petroleum hydrocarbons (TPH), and concentrations of selected polynuclear aromatic hydrocarbons (PAHs) are used for technical and practical reasons:
(1) The simple gravimetric measurement of TPH gives an estimate of all hydrocarbon compounds that may comprise residual oil. This method also includes the co-extraction of material that is not derived from petroleum such: as plant lipid material and waxes. At higher concentrations, the influence of non-petroleum products is not significant.
(2) The measurement of PAHs is singled out as a class of compounds of concern because they have been linked to acute and chronic toxicological effects. The distribution of individual PAH compounds gives insight into oil weathering or biologically mediated transformation. Quantitative measurement of PAHs is performed by gas chromatography and mass spectrometry (GC/MS). The results of the PAHs analysis can be used by both the biology team and the geology team for information on weathering, source fingerprinting, and persistence. Samples of both sediments and bio-tissue extractions are indicators of PAHs contamination. Detailed chemical analysis is required to confirm the presence of oil and differentiate it among the types of hydrocarbons detected in a monitoring study. Aromatic hydrocarbons are useful in differentiating crude petroleum from combustion byproducts. For instance, crude oil is characterized by PAHs composed primarily of 1-, 2-, and 3- ring aromatic compounds while PAHs compounds resulting from incomplete combustion are characterized by 3-, 4-, and 5- ring aromatic compounds. The ability of distinguishing between background aromatic hydrocarbons derived from natural events, such as fires, and residual oil pollution is achieved through the sensitivity permitted by GC/MS. The following list represents target compounds that should be assessed using GC/MS.
(nC-10 through nC-31)
hopanes (191 family)
sterenes (217 family)
Processes which affect the fate of oil released into an aquatic environment include: evaporation, dissolution, emulsification, absorption, photochemical, and microbial action. The rate at which these processes occur is controlled by the chemical composition and physical characteristics of the oil and the presence or absence of sufficient microorganisms along with the proper conditions for bioremediation to occur. Reduction in costs up to 90% can be achieved without great disruption of the natural habitat. 60% faster recovery of the bio-systems can be expected compared to conventional methods. All attempts should be made, if possible, to guard from damage or disruption of the natural habitat on beaches and marches during the initial coarse removal of heavy oil contamination. Ecosystems physically disrupted have delayed recoveries. Preliminary feasibility studies are usually not necessary unless the product has not been previously tested for efficacy. Products exist in the market which contains surfactants in addition to microbes that facilitate the dissolution of the oil from the substrate making it more available for the microbes to consume. In situ bioremediation studies are easily implemented on a contaminated beach and yield PAHs analysis results in a short period of time. The PAHs values, before and after biological treatment, can be compared to an adjacent untreated (control) area of the beach. These in situ studies have real visual and scientific verifiable impact on the benefits of bioremediation as a valuable tool to restore ecosystems after disasters such as the Horizon Oil spill.
© Frank Ramos, Save the Water, Inc.
[a] N. M. Fayad, et al., Effectiveness of a Bioremediation Product in Degrading the Oil Spilled in the 1991 Arabian Gulf War, 49 Bull. Environ. Contam. Toxicol. 787 (1992); P. H. Pritchard, et al., Oil Spill Bioremediation: Experiences, Lessons and Results from the Exxon Valdes Oil Spill in Alaska, 3 Biodeg. 15 (1992).
[b] NOAA Technical Memorandum NOS ORCA 114, 1997, Integrating Physical and Biological Studies of Recovery from the Exxon Valdez Oil Spill.